This invention relates to the method and apparatus for forming a can shell from sheet metal or sheet aluminum, for example, such as the methods and apparatus or tooling disclosed in U.S. Pat. Nos. 4,713,958, 4,716,755, 4,808,052, 4,955,223, 6,658,911 and 7,302,822. The disclosures of these patents are herein incorporated by reference to supplement the detail description of the present invention.
In such tooling assembly or apparatus, it has been found desirable for the apparatus to be constructed for use in a single action mechanical press such as disclosed in above mentioned U.S. Pat. Nos. 4,955,223 and 7,302,822 and to avoid using a double action mechanical press, for example, as disclosed in above-mentioned U.S. Pat. Nos. 4,716,755 and 6,658,911. A single action high speed press is simpler and more economical in construction and is more economical in operation and in maintenance and can be operated effectively and efficiently, for example, with a stroke of 1.75 inch and at a speed of 650 strokes per minute. There are also many more single action high speed presses in use in the field than there are double action presses.
It has also been found desirable for the apparatus or tooling assembly to incorporate an inner pressure sleeve and an outer pressure sleeve and to operate both sleeves with air pressure, but avoid actuating the inner pressure sleeve with circumferentially spaced and axially extending springs, for example, as disclosed in U.S. Pat. No. 7,302,822 or the use of circumferentially spaced and axially extending pins, for example, as disclosed in U.S. Pat. No. 4,716,755. The high speed axial reciprocating movement of the pins and the single piston which actuates the pins create undesirable additional heat, and is difficult to produce an adjustable and precisely controllable axial force on the inner pressure sleeve with the use of compression springs.
It is further desirable to have a precisely controllable constant force exerted by the outer pressure sleeve on the sheet material to avoid thinning the material between the outer pressure sleeve and the die core ring during high speed operation of the press. Precisely controllable air pressure on the inner pressure sleeve is also desirable for holding the chuckwall of the can shell while forming the countersink, panel wall and center panel of the can shell without thinning the sheet metal. In addition, it is desirable to minimize the vertical height of the tooling assembly for producing can shells in order to accommodate more single action high speed presses existing in the field and to operate at higher speeds with less heat being generated so as to avoid the use of water cooled tooling components. After reviewing the above patents, it is apparent that none of the patents provide all of the above desirable features.